Creating a spiral for film development....

This isn't so hard as it seems. I'm assuming that one doesn't have a genuine Minox developing tank. In my case I happened to have a spare Durst 35mm tank with a clear perspex spiral. I measured the depth of the flanges and calculated how much I would need to remove from the central spindle in order to comfortably hold the film and yet give plenty of access for solutions.

I cut through the spiral flush with the inner edge of one flange. I then measured the amount to be removed from the spindle and removed this with a fine saw; in fact I removed slightly less and then carefully filed the cut edge until the required spacing was obtained when the two parts were placed together.

The two parts were then joined by first adding some polystyrene cement to each face and offering them together. They were held together with a 'G' clamp for 24 hr. until the glue had set. As an additional precaution against separation, two small holes of a suitable diameter were drilled from the narrower face into the central spindle. The holes were tapped for a 2mm thread and two countersunk stainless steel screws were carefully inserted and tightened to provide extra security. The assembly has been dropped a few times but is still intact !

Here you can see the 'before' and 'after'.

Spirals before & after

Below is the complete tank assembly. The device with the spigot on one end is the spacer used to hold the spiral at the bottom of the tank when the lid has been fitted - see below.

Complete tank assembly

Inserting film needs a little practice. First of all, it's essential that the two flanges are dry. It helps to cut a little bit of film off the corners at the ends in order to produce a slight taper. Factory Minox film has rounded ends which has a similar effect. The film is carefully introduced into the spiral and slid around it. It will bind from time to time, but this can usually be overcome by gently tapping the spiral or even squeezing the flanges a little. With patience, the whole film will be introduced quite easily. I've had no problems at all with scratches even though one might think this could happen rather easily.

Once inside the tank, the spiral needs only 90ml of solution for complete coverage. To hold the spiral at the bottom of the tank (necessary as I use inversion agitation) I constructed a spacer from a cut down plastic 35mm film cassette container with a centrally placed peg to locate into the centre of the spiral - this was made out of a piece of plastic knitting needle. It might be thought of as a little 'Heath-Robinson' but it works, and at the end of the day, that's all that matters.... Obviously other developing tanks might be treated in a similar way with a little ingenuity.

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